The present invention is directed to an optical arrangement for the feedback-free coupling of a laser emission emitted by a semiconductor laser into an optical fiber. The arrangement includes a first optical lens and a second optical lens arranged following the first optical lens in a propagation direction of the emission, as well as an optical isolator being arranged in the beam path of the laser emission, the optical isolator being composed of a Faraday rotator and at least one polarizer, whereby the second lens is a component part of the Faraday rotator.
U.S. Pat. No. 4,966,444) application Ser. No. 07/137,080, filed Dec. 23, 1987), whose disclosure is incorporated herewithin by reference thereto and which corresponds to European EP 02 75 068 A2, discloses a feedback-free coupling arrangement for coupling a laser emission, which is emitted by a semiconductor laser, into an optical fiber. A blocking attenuation of approximately -35 dB can be achieved with this arrangement. Optical transmission systems that operate according to the heterodyne system require extremely monochromatic and frequency-stable laser transmitters and local oscillators. Lasers, whose spectral line is broadened due to feedback, cannot be utilized for this purpose (in this respect see a paper by R. W. Tkack and A. R. Chraplyvy "Linewidth broadening and mode splitting due to weak feedback in single-frequency 1.5 .mu.m lasers", Conf. on Fiber Comm. (OFC) '86, Atlanta, MI5; a paper by M. Shirasaki et al, "Optical Isolator for Single-Mode Fiber", European Conf. on Optical Comm. (ECOC) '86, Barcelona 1986, Vol. II, pp. 11- 16; and a paper by T. Chikama, H. Onaka, T. Kiyonaga, M. Suyama and H. Kuwahara, "An Optical FSK Transmission Experiment Using Solitary DFB Lasers for Broad-Band Distributed Networks", European Conf. on Optical Comm. (ECOC) '87, Vol. I, page 349, September 1987). A suppression of the feedback and, thus, a blocking attenuation of at least -70 dB is required here.